An embodiment of the present invention relates generally to multi-phase power switching converters, and more particularly, to multi-phase power switching converters having an interleaved mode for normal operating conditions and an all-phase mode for navigating transient conditions while maintaining adequate closed loop control.
Multi-phase power switching converters are often used in applications for receiving an input voltage source and outputting a shifted level voltage source. A plurality of output drivers may be connected to a single pulse width modulator (PWM). In addition, normal operating conditions for converters require the use of low duty cycles. Accordingly, a time division multiplexer (TDM) may be provided to separately and sequentially switch “on” and “off” each of the drivers to drive the output of the converter. Each of the drivers may be referred to as a “phase branch” of the converter.
The output voltage is determined by a maximum allowable duty cycle of the converter, which is determined by dividing the number of drivers into 100 (e.g., a three driver system has a 100/3 or 33⅓% duty cycle). During operation, the converter may encounter transient loading conditions, yielding slight deviations from the steady state of the output voltage. Often a transient condition will require the converter to exceed the maximum allowable duty cycle, which presents a problem for TDM-controlled converters.
One solution for negotiating transient conditions utilizes an empirical algorithm to hard-switch on all of the phase branches not, for that instant, selected by the TDM simultaneously with the TDM selected branch. Unfortunately, the phase branches in this approach are not subject to a closed loop transfer function that allows the transient response to be well-controlled.
It is desirable to provide a converter that satisfies system requirements for low duty cycles while maintaining well controlled closed loop feedback dynamics during the handling of transient conditions where the maximum allowable duty cycle of the converter must be exceeded.